Influence of hydrogen adsorption on the optical properties of the GaAs(100)-c(4×4) surface

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Abstract
We have investigated the influence of hydrogen adsorption on the optical anisotropy and the surface reconstruction of the GaAs(100)-c(4×4) surface using reflectance difference spectroscopy (RDS) and low-energy electron diffraction (LEED), respectively, At low exposures the optical anisotropy of the c(4×4) surface is removed almost completely by hydrogen adsorption due to removal of the As dimers in the outermost As layer, while the LEED pattern changes from c(4×4) to (1×1). At intermediate hydrogen exposures, the surface again becomes optically anisotropic showing the signature of Ga dimers in the RDS spectra, while LEED indicates a mixture of (1×2) and (√2 × √2 ) reconstructions. Finally, at even higher dosages the Ga dimers are broken by hydrogenation. The LEED pattern shows a (1×1) symmetry and the RDS features are correlated with the critical points of the bulk electronic band structure.